Removed left over debug output.
Fix possible problem with negative mQueuedCommands

mQueuedCommands was unsigned, but can become shortly negative.
Unfortunately this means I had to remove the assert that
keeps track of possible errors, but I believe that already
has been proven that it works anyway.

The reason it can become negative is because its meaning is
"Number of added ADD (request) commands minus number of REMOVE (request)
commands". Hence, it is incremented when an ADD command is added to the
queue and decremented when that ADD command is removed from the queue.
However, it is first decremented when a REMOVE command is added to the
queue and then incremented again when that REMOVE command is removed
again from the queue. Such a remove command is current extremely rare:
it only happens when curl fails to time out - and the backup timeout of
the statemachine fires after 10 minutes of a curl request being idle.
That should normally only happen if a request never reached curl of
course, and is queued in the curl thread, waiting to be added to curl,
aka: -0-0-1,{...} for 10 minutes...

Now that, in turn should be impossible (since the "don't count long poll
connections) unless the Curl* Debug Setting variables are changed to
wrong values.. but ok, can only guess here.